1. Field of the Invention
The present invention relates to a display panel, and more particularly, to a display panel having sub-pixels with a specific polarity arrangement.
2. Description of the Prior Art
In general, liquid crystal displays have been widely applied to various kinds of portable information products, such as notebook and personal digital assistant (PDA), in the market, because of having the advantages of light weight, low power consumption and low radiation. When liquid crystal in the liquid crystal display is fixed at an angle too long during driving the liquid crystal display, the liquid crystal has permanent deformation, and a frame displayed by the liquid crystal display cannot change. In order to avoid reducing the display quality of the liquid crystal display, a polarity inversion driving method is generally used in the liquid crystal display.
The conventional polarity inversion driving method can be divided into a frame inversion, a row inversion, a column inversion, and a dot inversion. Referring to FIG. 1 is a schematic diagram illustrating a polarity arrangement of sub-pixels in the liquid crystal display driven by a column inversion driving method according to the prior art. As shown in FIG. 1, the liquid crystal display 10 of the prior art includes a plurality of sub-pixels 12, arranged in a matrix formation, and the polarity arrangement of the sub-pixels disposed in the same row is that one positive polarity and one negative polarity respectively arranged in turn, and the sub-pixels disposed in the same column have the same polarity. In addition, the sub-pixels in each column respectively are red (R) sub-pixels, green (G) sub-pixels, and blue (B) sub-pixels in turn, and each red sub-pixel, each green sub-pixel adjacent to the red sub-pixel and each blue sub-pixel adjacent to the green sub-pixel constitute a pixel 18. In a next frame, a polarity of each sub-pixel 12 is changed into an opposite polarity, i.e. the original positive polarity is changed into the negative polarity, and the negative polarity is changed into the positive polarity. Accordingly, the liquid crystal can be avoided having permanent deformation due to fixing at an angle too long.
However, during testing the liquid crystal display, the liquid crystal display turns off a part of pixels so as to display a frame with a bright column and a dark column arranged sequentially in a row direction, and the frame shows white image. In this driving method, the red sub-pixels and the blue sub-pixels, which are turned on, disposed in a first row have the positive polarity, and the green sub-pixels, which are turned on, disposed in the first row have the negative polarity. Furthermore, the polarity of each sub-pixel is determined by comparing the voltage of the pixel electrode of each sub-pixel with a common voltage. For this reason, when the voltage of the pixel electrode of each sub-pixel is higher than the common voltage, the polarity of the sub-pixel is the positive polarity, and the voltage of the pixel electrode is at a high level. Otherwise, the polarity of each sub-pixel is the negative polarity, and the voltage of the pixel electrode is at a low level. When the number of the sub-pixels having the positive polarity is larger than the number of the sub-pixels having the negative polarity, i.e. the pixel electrodes of the major sub-pixels have the voltage at the high level, the value of the common voltage is easily affected by the voltage of the pixel electrode to be shifted toward the voltage at the high level. Thus, a voltage difference for driving the red sub-pixels and the blue sub-pixels is reduced, and a voltage difference for driving the green sub-pixels is increased, which result in a gray scale displayed by the green sub-pixels being higher than gray scales displayed by the red sub-pixels and the blue sub-pixels. For this reason, the liquid crystal display easily generates a greenish frame during testing.
In order to avoid generating greenish frame during testing the liquid crystal display, a method of using inverters to change the polarity arrangement of the sub-pixels is disclosed. Refer to FIG. 2. FIG. 2 is a schematic diagram illustrating a polarity arrangement of the liquid crystal display panel using inverters to change the polarities of the sub-pixels according to the prior art. As shown in FIG. 2, a data-line driving circuit 22 of the liquid crystal display panel 20 includes an inverter 24, a first driving circuit 26 and a second driving circuit 28. An end of the inverter 24 is coupled to the first driving circuit 26, and the other end of the inverter 24 is coupled to the second driving circuit 28. The inverter 24 is used to invert the polarities of data signals inputted into the first driving circuit 26 and the data signals inputted into the second driving circuit 28. Accordingly, in the same row, the red sub-pixel 30 in the first column and the red sub-pixel 30 in the seventh column have the polarities opposite to each other. Similarly, the green sub-pixel 32 in the second column and the green sub-pixel 32 in the eighth column have the polarities opposite to each other, and the blue sub-pixel 34 in the third column and the blue sub-pixel 34 in the ninth column have the polarities opposite to each other. Therefore, in all sub-pixels that are turned on, the number of the sub-pixels having the positive polarity is the same as the number of the sub-pixels having the negative polarity, and the common voltage does not shift.
Nevertheless, for changing the polarity of the sub-pixel, the liquid crystal display panel of the prior art should divide the pixel region into two parts. One is connected to a first driving circuit, and the other one is connected to a second driving circuit. An inverter should be coupled to the first driving circuit and the second driving circuit, so that the polarity provided by the first driving circuit is opposite to the polarity provided by the second driving circuit. Accordingly, since the inverter should be extra added into the liquid crystal display panel, the cost of the liquid crystal display panel is increased, and the complexity of the data driving circuit is also increased. Besides, a driving chip for controlling the liquid crystal display panel already has the inverter, and is disposed outside the liquid crystal display panel. Thus, the liquid crystal display panel added with the inverter further limits the design of the driving chip.